Gas Exchange in Bony Fish in a Snap! Unlock the full A-level Biology course at http://bit.ly/2Z8lazL created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University.

The key points covered of this video include:

1. The Tracheal System
2. Gas Exchange in the Trachea
3. Ventilating the Tracheal System

The Tracheal System

Insects are small organisms but tend to be highly active. One common featyre shared by all insects is their waxy exoskeleton that helps them with protection and water retention. Waxy exoskeletons don’t allow for effective gas exchange. Toovercome this issue insects evolved an exchange surface - called a tracheal system - that delivers oxygen directly to every tissue in the body.

Exchange in the Trachea

Gas exchange in the tracheal system occurs mostly through the tracheal fluid at the ends of the tracheoles. When resting the liquid seeps into the tracheoles from the surrounding cells. When the insect is active the muscles draw up the tracheal fluid which: Provides them with oxygen containing fluid for respiration, lowers the pressure in the tracheoles which draws more air in through the spiracles, increases the surface area available for oxygen to diffuse through tracheal walls directly.

Ventilating the Tracheal System

Larger insects are able to ventilate their tracheal system and have evolved several different mechanisms for doing so: Air sacs in the tracheal system can be squeezed by flight muscles to push air in and out, flight muscles can alter the volume of the insect thorax to ventilate the tracheal systems, Some insects have evolved a specialised breathing mechanism, as they expand their abdomen they close spiracles at the back end of their body, When they contract their abdomen they open up the spiracles at their rear and close those at the front.

Summary

Insects have an exchange surface that delivers oxygen without the need for blood and within the constraints of an exoskeleton
The tracheal system delivers oxygen to every tissue in an insects body
Insects can regulate their rate of gas exchange through adjusting the amount of tracheal fluid in their tracheoles
Some insects can ventilate their tracheal system through movements of their body and additional specialised mechanisms